From the viewpoint of ensuring light weight and stiffness, sandwich panels made from resin are adopted for various purposes.
The resin sandwich panel may include two skin material sheets of resin and a thermoplastic resin core material disposed between the skin material sheets. The surfaces of the thermoplastic resin core material are adhered to the corresponding skin material sheets of resin by face-to-face bonding. As disclosed in Japanese Unexamined Patent Application Publication No. 2010-174577A, from the viewpoint of further ensuring stiffness, a reinforcement member may be provided between the skin material sheets and integrally bonded with the thermoplastic resin core material.
More specifically, the thermoplastic resin core material is of split type, and the reinforcement member is an H-shaped extrusion reinforcement. The reinforcement member is disposed between adjacent split portions of the thermoplastic resin core material and has a first recess opening on one side and a second recess opening on the other side. The thermoplastic resin core material is provided at an end portion thereof with a protrusion which has a length equal to or greater than a predetermined length of the reinforcement member and which can be laterally press-fit into the recess. In order to make the reinforcement member flush with the thermoplastic resin core material, the protrusion is formed of an engaging step portion which is a recessed portion of the end portion of the thermoplastic resin core material.
Japanese Unexamined Patent Application Publication No. 2010-174577A discloses various modes for enabling press-fitting between the reinforcement member and the thermoplastic resin core material.
More specifically, in one type that is disclosed, one and/or the other of mutually opposed ends in the opening of the reinforcement member is provided with a hook-shaped portion extending in an opening-narrowing direction. Correspondingly, the protrusion of the thermoplastic resin core material is provided with a groove in which the hook-shaped portion can engage.
In another type disclosed, the recess of the reinforcement member is provided with a number of narrow ridges extending in the longitudinal direction.
In yet another type disclosed, the protrusion of the thermoplastic resin core material has a notch.
However, such conventional reinforcement member-equipped sandwich panel has the following technical problems, due to size variations during the molding of the resin core material.
First, it is difficult to press-fit the reinforcement member with respect to the molded resin core material.
More specifically, when the resin core material, particularly a solid foamed resin core material, is molded, there are size variations in the thickness direction. Accordingly, if the thickness of the protrusion is set greater than the interval of the inner surfaces of the recess throughout in the longitudinal direction thereof, it may become difficult to press-fit the resin core material into the reinforcement member in the case of a maximum dimensional tolerance.
Secondly, it is difficult to integrally hold the molded resin core material and the reinforcement member, posing a problem in efficient manufacture of the resin sandwich panel.
More specifically, if the thickness of the protrusion is set uniformly throughout in the longitudinal direction thereof, the reinforcement member may fall from the resin core material in the case of a minimum dimensional tolerance, as opposed to the first case. The process of manufacturing the resin sandwich panel is conventionally performed as follows. Between split molds, two resin sheets in molten state are disposed. The reinforcement member and the resin core material are made into an integral component, which is then set on an insert robot. The insert robot positions the integral component with respect to the resin sheets, and the split molds are clamped.
Accordingly, in order to make the reinforcement member and the resin core material into an integral component, a separate step is required to adhere the reinforcement member and the resin core material to each other using a hot melt adhesive, for example. This may pose a problem in efficient manufacture of the resin sandwich panel.